Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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3 resultados
Resultados da Pesquisa
- Surface integrity analysis in the super duplex stainless steel ASTM-A890 after machining(2008) Bordinassi E.C.; Stipkovic M.F.; Batalha G.F.; Delijaicov S.; De Lima N.B.The purpose of this paper was to study the main effects of the turning in the superficial integrity of the duplex stainless steel ASTM A890-6A. The tests were conducted on a turning centre with carbide tools and the main entrances variables were: tool material class, feed rate, cutting depth, cutting speed and cutting fluid utilisation. The answers were analysed: microstructural analysis by optical microscopy and x-ray diffraction, cutting forces measurements by a piezoelectric dynamometer, surface roughness, residual stress by x-ray diffraction technique and the microhardness measurements. The results do not show any changes in the micro structural of the material, even when the greater cutting parameters were used. The smaller feed rate (0.1 mm/v), smaller cutting speed (110 m/min) and the greater cutting depth (0.5 mm) provided the smaller values for the tensile residual stress, the smaller surface roughness and the greater microhardness. Copyright © 2008 Inderscience Enterprises Ltd.
- Stress relief by sub-harmonic vibrations: Analysis and parametrization Alívio de tensões por vibrações sub-ressonantes: Análise e parametrização(2018) Martins C.A.P.; Morilla J.C.; Marques P.V.; Delijaicov S.© 2018, Universidade Federal do Rio de Janeiro. All rights reserved.The worldwide industries use the sub-resonant vibration stress relief for over twenty years. In Brazil, this technic has been used for about fifteen years. In the last years, with the searching of new alternatives process aiming energy economy with consequently the Global Heating reduce, the use of this technique can be very interesting. Moreover, the time reduction between vibration and thermal stress relief processes is around 80%, allowing a faster repairing pieces, which is prime factor to make a maintenance stop in a short time. Meanwhile, the scientific literature is rare about the use and the efficacy of this system. This work has the propose of comparing the results of sub-harmonic stress relief process with conventional thermal process and correlate them to the decrease of the resonance peak frequencies, comparing before and after treatments. This work introduces some examples of successful works made at industry and presents an experimental research to measure the residual stress, before and after the treatment, comparing to the conventional heat treatment results. This work shows generally the stress relief by sub-resonant vibrations in the 0.2 mm depth, promotes stress relief on average 10% higher when compared with the results obtained by the conventional heat treatment.
- Characterization of the surface and mechanical properties of the friction stir welding in tri-dissimilar joints with aluminum alloys and titanium alloy(2018) Delijaicov S.; Yakabu D.Y.; De Macedo B.; Resende H.B.; Batalha M.H.F.© 2017, Springer-Verlag London Ltd., part of Springer Nature.The search for lighter and more resistant structures contributed to the development of effective welding methods. Among them, friction stir welding, a recent technique patented in 1991, in which welding is performed by the friction between a rotating tool and the materials to be welded, has widely been studied in the last decades. Among the advantages the technique provides, are the possibility of welding aluminum alloys series 2xxx and 7xxx, and the possibility of welding materials of different chemical compositions. The industry is still cautious about using this technique, yet several studies have been performed to improve knowledge on it. This research investigated the three dissimilar junctions between aluminum alloys 2024-T4 and 7475-T6 with titanium alloy Ti6Al4V. The aluminum alloys were positioned on the top portion of the welding creating a butt weld. The titanium alloy was placed on the bottom portion of the weld creating a lap welding with the aluminum alloy. The parameters of rotation, welding speed, and tilt were varied, following a central composite experimental design. Through the response surface analysis, it was possible to identify the correlation between the input and output parameters. This correlation is used to identify main influence between the parameters and can be used to optimization of the process. The influences of these parameters were evaluated on the welding surface by measuring residual stress and microhardness. The residual stress was analyzed by the hole drilling method on the aluminum side and by X-ray diffraction on the titanium side. The microhardness was analyzed by the Vickers test. On the aluminum side, residual stress and microhardness show a strong relation; high value of residual stress resulted in low value of microhardness. On the titanium side, residual stress shows a relation with temperature; the high value of temperature resulted in low value of stress. The tensile test was used to compare joint efficiency between different welding parameters and the base metal. It was possible to reach parameters in which the welding ultimate tensile stress exceeded the AA2024 value.